Abstract:

Connector assembly for connecting and/or disconnecting an electric power
cable (1) to/from a subsea pipeline (8), in particular for direct
electric heating (DEH) thereof, comprising: a female cone element (6)
mounted (2) to the pipeline (0) surface, a complementary male cone
element (5) attached to an end of the power cable (1), and bolt
tightening means (70) for securing contact between the female cone
element (6) and the male cone element (5).
The tightening means (70) comprises in a first stab member (7) adapted to
be received in a first receptacle (16) in said female cone element (6),
said first receptacle (16) has an opening facing in opposite direction of
the cone (12) of the female cone element (6) for receiving said first
stab member (7), and a tightening bolt (7a) is provided in said first
stab member (7) with an inner end (7c) of the bolt (7a) being adapted to
engage said male cone element (5) and with an outer end (7b) being
accessible for the connecting and/or disconnecting operations.

Claims:

1. Connector assembly for connecting and/or disconnecting an electric
power cable (1) to/from a subsea pipeline (8), in particular for direct
electric heating (DEH) thereof, comprising:a female cone element (6)
mounted (2) to the pipeline (8) surface,a complementary male cone element
(5) attached to an end of the power cable (1), andbolt tightening means
(70) for securing contact between the female cone element (6) and the
male cone element (5),characterised in thatsaid tightening means (70)
comprises a first stab member (7) adapted to be received in a first
receptacle (16) in said female cone element (6),said first receptacle
(16) has an opening facing in opposite direction of the cone (12) of the
female cone element (6) for receiving said first stab member (7), and a
tightening bolt (7a) is provided in said first stab member (7) with an
inner end (7c) of the bolt (7a) being adapted to engage said male cone
element (5) and with an outer end (7b) being accessible for the
connecting and/or disconnecting operations.

2. Assembly according to claim 1, wherein said first receptacle (16) is
coaxial with the cone (12) of the female cone element (6), and the
tightening bolt (7a) is located centrally in said first stab member (7).

3. Assembly according to claim 1 or 2, wherein a threaded portion (7c) of
said tightening bolt (7a) is adapted to engage corresponding threads in
the male cone element (5).

4. Assembly according to any one of claims 1-3, wherein a central cavity
in said first stab member (7) contains an axial compression spring (17)
cooperating with a stopper element (18) on a middle portion of said
tightening bolt (7a), so as to provide a degree of resiliency of the bolt
in the axial direction.

5. Assembly according to any one of claims 1-4, wherein a second stab
member (3) is mounted on said male cone element (5) and is adapted to be
received in a second receptacle (4) rigidly connected (2) to the pipeline
(8).

6. Assembly according to claim 1 or 5, wherein said first and/or second
stab member(s) (7,3) is/are provided with ball locking means
(19,20/13,15) with ball grooves (20,15) having a certain extension in the
axial direction of said stab member(s) so as to allow for some resilient
free play of the stab member(s) axially when inserted into the
corresponding receptacle(s).

7. Assembly according to any one of claims 1-6, wherein a contact surface
at the inner end of said male cone element (5) is provided with ribs or
corrugations (5a) for improving the electric contact to be secured.

8. Assembly according to any one of claims 1-7, wherein said first and
second stab members (7,3) are provided with ROV (WROV) handles (27,23)
for cooperation with said ROV or WROV.

9. Method for connecting an electric power cable (1) to a subsea pipeline
(8) employing a connector assembly comprising a female cone element (6)
mounted to the pipeline surface,a complementary male cone element (5)
attached to an end of the power cable (1), andbolt tightening means (70)
for securing contact between the female cone element (6) and the male
cone element (5),characterised by the following steps:an ROV or WROV
grips (50) a main (or second) stab member (3) incorporating said male
cone element (5), and inserts the male cone element (5) into the cone
(12) of said female cone element (6),an ROV or WROV grips (50) an
auxiliary (or first) stab member (7) comprised by said tightening means
(70), and inserts the auxiliary stab member into a receptacle (16) in
said female cone element (6) opposite of said cone (12) of the female
cone element, andan ROV or WROV operates said tightening means (70) so as
to secure contact between the female cone element (6) and the male cone
element (5).

10. Method according to claim 9, wherein all said steps are performed by
one and the same ROV or WROV.

Description:

[0001]The present invention relates to a connector assembly for connecting
and/or disconnecting an electric power cable to/from a subsea pipeline,
as well as a corresponding method. Such connector will comprise a female
cone element mounted to the pipeline surface, a complementary male cone
element attached to an end of the power cable, and bolt tightening means
for securing contact between the female cone element and the male cone
element.

[0002]What is aimed at, is a quick and safe way to connect and disconnect
an electric power cable to a pipeline by use of an ROV (remote operated
vehicle--or possibly WROV--work remote operated vehicle). After
connection of the cable, a current for example of about 3000 ampere, will
be fed to the pipeline, in particular for DEH purposes (DEH: Direct
Electrical Heating).

[0003]GB 2357910 for such a purpose describes the use of a cone system
comprising elements substantially as mentioned above, and more
specifically discloses a repair concept for connecting a spare (single
conductor) cable to an already installed connection plate at the
pipeline. This is accomplished by using a pull-in wire through the
connection plate and cutting away the pull-in wire after installation.
Such a repair cable cannot be disconnected any more, i.e. this is a
permanent connection which is not usable as a short-time connection since
no disconnection is possible. The existing high voltage connectors are
too large in size and need a large connection tool/skid to be mated.

[0004]Of primary interest in connection with the present invention is a
short-time or temporary (typically for 14 days) connection of a power
cable to a pipeline. The cable (usually single conductor) is to be
operated from a vessel and can be both connected to and disconnected from
the preinstalled connection plate on the pipeline. Such an operation will
be performed by means of an ROV (or WROV), and should be as fast and
simple as possible. It is to be noted that temporary heating of pipelines
with a power source and cable installation from a ship as contemplated
here, has not been performed before.

[0005]An object of the present invention is to use an ROV (or WROV)
operated stab and receptacle connection, as known in the principle per
se, and incorporate a novel and specific concept with a spline cone
connection mated up by use of a stab-in-bolt/rotatable element that will
be tightened by the ROV (or WROV).

[0006]In a connector assembly as referred to above, the novel and specific
features according to the invention are primarily characterised in that
said tightening means comprises a first stab member adapted to be
received in a first receptacle in said female cone element, said first
receptacle has an opening facing opposite of the cone of the female cone
element for receiving said first stab member, and a tightening bolt is
provided in said first stab member with an inner end of the bolt being
adapted to engage said male cone element and with an outer end being
accessible for the connecting and/or disconnecting operations.

[0007]Additional features are spelled out in dependent claims directed to
the assembly, as well as in the method claims (claims 9-10).

[0008]The foregoing and other objects, features and advantages of the
present invention will become more apparent in the following detailed
description of preferred embodiments as illustrated in the accompanying
drawings, of which:

[0009]FIG. 1 in axial cross-section schematically shows a
cable-to-pipeline connector assembly according an embodiment of the
present invention, and

[0010]FIG. 2 schematically illustrates main method steps that may be
performed when establishing a connection with an assembly as shown in
FIG. 1.

[0011]FIG. 1 shows an electric power cable 1, comprising for example a
single core conductor, on which there is crimped an electrical male cone
element 5. Around the cone element 5 there is mounted a main (or second)
stab member 3 fitting into a receptacle 4 that constitutes a docking
station for this stab member. Docking receptacle 4 is carried by a
connection plate 2 which is welded or otherwise anchored to the surface
of a pipeline 8.

[0012]In order for the stab member 3 to be securely held in receptacle 4
there is provided ball locking means with balls 13 adapted to lock into a
peripheral groove 15, as known per se. However, a specific feature at
this point is seen in the somewhat elongate shape of the groove 15 in the
axial direction. Thus, the stab member 3 has some degree of free play in
the in the length direction with respect to receptacle 4 when inserted
therein.

[0013]A female cone element 6 being of complementary shape to the above
male cone element 5, is provided in the form of a small receptacle welded
to the connection plate 2. In the embodiment shown, female cone
element/receptacle 6 extends through plate 2, whereas receptacle 4 abuts
plate 2. With such a structure or relative arrangement of essential parts
incorporated in the connector assembly, these parts are located very
close to and are rigidly supported by the connection plate 2.

[0014]The end of the male cone element 5 has a "corrugated" contact
surface 5a to provide a good electrical contact with the female cone
element 6. Such contact improving corrugations may for example take the
form of ribs on the conical surface of the male and/or female cone
element.

[0015]The parts that are preinstalled (connection plate 2, docketing
receptacle 4 and the small receptacle/female element 6) on the pipeline 8
are few and do not have any moveable subparts. They are designed to be
easy to clean and to be protected by caps. The parts can be coated with
thermal insulation in order to minimize the pipeline heat loss.

[0016]The parts that are movable in order to establish an electrical
connection as explained above, are at one hand the male cone element 5
with its main (or second) stab member 3, and at the other hand tightening
means for bringing about and maintaining a close electrical (and
mechanical) contact between the male and female elements.

[0017]Such tightening means 70 here comprises an auxiliary (or first) stab
member 7 that fits into a receptacle 16 at the outer or rear end of the
female cone element 6. Centrally in stab member 7 there is provided an
axial bolt 7a for the tightening to be effected. Thus, the inner end 7c
of bolt 7a is threaded and adapted to engage internal threads at the end
of male element 5. For rotating bolt 7a an outer end 7b of the bolt is
accessible outside stab member 7.

[0018]As will be seen from FIG. 1, there is a central cavity 9 formed in
the first stab member 7, accommodating a compression spring 17 that
serves to give bolt 7a, with a stopper element 18, some degree of
resiliency lengthwise. This is in order for the inner bolt end 7c, in
particular, to be less vulnerable to impact and damage during
installation, before being threadedly engaged with the male cone element
5.

[0019]Like the second stab member 3 also the first stab member 7 has a
ball locking mechanism 19/20 so as to allow for some free play in
relation to female receptacle 6 before tightening as described above.
Each of the stab members 3 and 7 has a ROV handle 23 and 27,
respectively.

[0020]Usually the male cone element 5 will be made of copper and the
female cone element 6 of steel. This choice of materials is primarily in
view of the subsea environment affecting the structures concerned.
Reliability is very important, in particular with respect to the
structural parts being preinstalled on the pipeline; an approximate
design life of about 50 years at water depths roughly from around 550
meters to around 850 meters may be aimed at in a practical installation.

[0021]For illustrating method steps when installing an electric cable 1 at
a pipeline 8, reference is made to FIG. 2.

[0022]STEP 1: An ROV or WROV with its manipulator arm and claw tool 50
takes up male cone element 5 with stab member 3, having been lowered
together with the connected cable 1, from a supply vessel (not shown) to
the seabed close to the pipeline 8 and its connecting plate 2. The end of
cable 1 with stab member 3 is being held above the seabed by means of
buoyancy modules 100 attached to the cable. From this position the ROV or
WROV guides the male cone/stab 5/3 into the receptacle 4 on the
connection plate 2. Here the stab is self-locking in the receptacle as
described above, by locking means 13/15.

[0023]STEP 2: The same (or another) ROV (or WROV) then by means of handle
27 picks up the other stab member 7 with the tightening means 70 and
inserts it in the receptacle 16 formed in the female cone element 6, from
the opposite side in relation to cone 12 and with a self-locking function
19/20 so as to temporarily keep the parts assembled.

[0024]STEP 3: Finally, in order to establish a secure contact between the
male and female cones, the same (or another) ROV (or WROV) with its tool
50 or possibly a special tool engaging outer bolt end 7b, will rotate the
bolt 7a to screw the same into the end of the male cone 5, thereby
pulling the two parts together, into the position shown in FIG. 1.

[0025]For removing an electrical connection established according to
method steps as described above, the ROV (or WROV) in a position
corresponding to STEP 3 in FIG. 2, should unscrew bolt element 7a in
order to disconnect the female and male cones 6 and 5. In this operation
it is to be recalled that cone/stab 5/3 has a free play in the length
direction related to receptacle 4, thus making it easier to free the
cones.

[0026]From a position corresponding to STEP 1 in FIG. 2, the ROV (or WROV)
can then pull out cone/stab 5, 3 and cable 1. The ROV (or WROV) can also
use high torque in order to disconnect the cones. In general it will be
understood that a disconnect operation will be effected in a reverse
sequence of steps compared to connecting STEPS 1, 2 and 3 described
above.

[0027]In the context of direct electric heating (DEH) it is a normal
procedure to provide for a similar connect/disconnect ROV operation at an
opposite end of the DEH cable at a remote point on the pipeline.

[0028]The present invention provides advantageous solutions for temporary
heating of pipelines where the DEH cable is to be disconnected after use.
Using the ROV or WROV operated stab/receptacle solution together with a
new design of electrical cone elements/tightening means represents a new
concept for quick connection/disconnection of power cables to pipelines.